Transmitting or receiving device comprising a dipole antenna

ABSTRACT

553,636. Wireless receiving and transmitting circuits. PHILIPS LAMPS, Ltd. (Naamlooze Vennootschap Philips&#39; Gloeilampenfabrieken). Nov. 26, 1941, No. 15247. [Class 40 (v)] A circuit for coupling a dipole antenna 4 to a transmission line connected to terminals 1, 2, with or without a transformer 8, so as to ensure correct matching over a wide frequency band, comprises a resistance in two parts 5, 6 which together equal the radiation resistance of the antenna, tapped on to a resonant circuit 7 tuned to the natural frequency of the antenna 4. The tappings are chosen so as to include an inductance which is equal to the capacity of the antenna multiplied by the square of the radiation resistance. With these conditions the arrangement presents at the terminals 1, 2 an impedance which is a pure resistance equal to the radiation resistance of the antenna over a wide band of frequencies.

March 30, 1943.

TRANSMITT I NG OR. RECEIVING DEVICE COMPRISING DIPGLE ANTENNAS FiledJan. 21, 1942 Jim 1 L [55- 55. At] N V'VV' INVENTOR ATTORNEY PatentedMar. 30, 1943 TRAN SlVIITTIN G OR RECEIVING DEVICE COMPRISING A DIPOLEANTENNA Adelbcrt van Weel, Eindhoven, Netherlands; vested in the AlienProperty Custodian Application January 21, 1942, Serial No. 427,554 Inthe Netherlands August 1, 1940 2 Claims.

This invention relates to a device for transmitting electricoscillations by means of a dipole antenna that through a transmissionlead can be connected to a high frequency energy transducer such astransmitter or receiver and is particularly useful when a wide frequencyband is to be transmitted by the antenna, for example for televisionpurposes.

The object of the invention consists in ensuring correct matching of thedipole antenna to the transmission lead throughout a wide frequencyband.

According to the invention, for this purpose the conductors whichconnect the dipole antenna, in some cases through a transformer, to thetransmission lead have arranged between them the series combination ofan ohmic resistance equal to the radiation resistance of the antenna anda parallel resonance circuit which is tuned to the natural frequency ofthe antenna and whose effective inductance is equal to the capacity ofthe antenna multiplied by the square of the radiation resistance.

In order that the invention may be clearly understood and readilycarried into effect it will now be described more fully with referenceto the accompanying drawing, wherein Figur 1 shows a substitutiondiagram of an antenna system in which is embodied the present inventionand Figure 2 shows a modification thereof.

Referring to Figure l, the inductance L, the capacity C and theresistance R constitute the substitution diagram of a dipole antennasince a dipole antenna behaves as regards frequencies adjacent theresonance frequency as a series rescnance circuit. Via the terminals land 2 the dipole antenna may be connected to a transmission lead 3, atransformer being inserted, if necessary, in order to match the waveresistance of the lead to the radiation resistance R of the antenna.

It is obvious that correct matching is only possible in connection withthose frequencies with which the impedance of the antenna isapproximately real, that is to say, only in connection with acomparatively narrow frequency band immediately adjacent the resonancefrequency of the antenna correct matching will be ensured.

According to the invention, in order to enable matching in a widefrequency band the conduc tors which connect the antenna to theterminals I and 2 have connected between them a network comprising theseries combination of an ohmic resistance R1 and a parallel resonancecircuit L1C1.

If the conditions are satisfied a pure real impedance the value of whichis R is measured between the terminals l and 2 as viewed from the lead 3for any frequencies.

The value of the inductance L1 derived from the above conditions is inpractice frequently too low for an efficient construction of theoscillatory circuit LlCl. This difficulty may be obviated byconstructing the oscillatory circuit so as to have a higher inductanceand by connecting the resistance R1 to a tapping of the circuit. In thiscase, the effective inductance of the oscillatory circuit is to beunderstood to mean the inductance of the transformed oscillatory circuitwhich appears to occur in series with the resistance R1.

From the point of view of symmetry it is preferable to split up theresistance R1 into two equal parts which are arranged on either side ofthe oscillatory circuit.

An embodiment of the invention, modified as suggested above, is shown inFigure 2. In this case, a dipole antenna 4 is connected through atransformer 8 to the terminals 1 and 2 to which a transmission lead canbe connected, the transformer 8 serving for matching the radiationresistance of the antenna 4 to the wave resistance of the transmissionlead.

The conductors which connect the antenna to the primary of thetransformer 8 have arranged between them two .equal resistances 5 and 6which jointly are equivalent to the radiation resistance of the antennaand whose adjacent ends are connected to two tappings of an oscillatorycircuit 1 symmetrically arranged relatively to the midpoint. The circuitI is tuned to the natural frequency of the antenna 4 and the inductanceof the transformed oscillatory circuit that appears to occur between thetwo tappings is equal to the capacity of the antenna multiplied by thesquare of the radiation resistance.

Between the terminals l and 2 a constant and real impedance is measuredthroughout a wide frequency band on either side of the natural frequencyof the antenna.

It may be observed that the ratio between the antenna-E. M. F. and thevoltage occurring between the terminals l and 2 still depends on thefrequency. This frequency relation may be annulled if desired by asuitable choice of the frequency characteristic of the transmitter orreceiver. &

I claim:

1. In an antenna system, an antenna and high frequency transducer meanscoupled to terminals of said antenna, a circuit including a capacity andan inductance connected in parallel and tuned to the operating frequencyof said antenna, tapping points on said inductance including less thanall of said inductance therebetween so located that the reactancebetween said tapping points is numerically equal to the product of thecapacity of said antenna and the square of the radiation resistance ofthe antenna, and a series circuit including an ohmic resistance equal tothe radiation resistance of said antenna and the portion of saidinductance between said tapping points connected across the terminals ofsaid antenna.

2. In an antenna system, an antenna and high frequency transducer meanscoupled to terminals of said antenna, a circuit including a capacity andan inductance connected in parallel and tuned to the operating frequencyof said antenna, tapping points on said inductance including less thanall of said inductance therebetweenso located that the reactance betweensaid tapping-'points is numerically equal to the product of the capacityof said antenna and the square of the radiation resistance of theantenna, and a series circuit including an ohmic resistance equal to theradiation resistance of said antenna and the portion of said inductancebetween said tapping points connected across the terminals of saidantenna, said ohmic resistance being split into two equal parts, oneconnected to each inductance tapping point.

ADELBERT VAN WEEL.

